The objective of this research program is a comprehensive, systematic, and parametric evaluation of developing auditory perceptions in an animal model. Naturalistic and arbitrary sounds are presented to subjects exposed to normal and atypical perinatal experiences. Developing sensory attributes will be inferred from psychophysical scaling procedures that create maps of neonates' responses to changes in auditory stimuli. Delays in the otherwise regular peeping of newborn chicks are used as measures of the extent to which various stimuli are perceived as similar or different. Controlled signal detection analyses will determine if absolute thresholds to pure tones and a naturalistic stimulus change over the first few postnatal days. Signal detection analyses will evaluate both frequency and temporal discriminations in these neonates. A series of manipulations will assess the effects of perinatal noise, prenatal ethanol, and premature hatching on measures of perception. If these manipulations affect sensory attributes but not habituation detection, or discrimination, then atypical perinatal experience will be shown to cause deficits in higher order, more subtle attentional ind perceptual processes. This research program will contribute to an understanding of the roles of early experience in the development of auditory perception. This research may also contribute to an understanding of the effects of atypical experiences on perceptual development in human neonates. Manipulations include conditions experienced by increasing numbers of human neonates, and the outcome measures are relevant to human neurobehavioral development. A collaboration of scientists trained in psychoacoustics and human development will maximize the opportunity to find general principles of perinatal behavioral development.